1. Field of the Invention
The present invention relates generally to a suspension control system for an automotive vehicle, for regulating vehicular attitude. More specifically, the invention relates to an anti-squat suspension control system which can suppress squat or nose-up upon vehicular accleration. Particularly, the invention relates to anti-squat suspension control system which is active for suppressing squat when vehicle starts to run and/or demand for vehicular acceleration in a greater magnitude occurs.
2. Description of the Background Art
Japanese Patent First (unexamined) Publication (Tokkai) Showa No. 58-116215 discloses an anti-squat suspension control system. The disclosed system has a control unit connected to a throttle angle sensor, a vehicle stopping condition detector or brake switch and a vehicle speed sensor to receive therefrom a throttle angle indicative signal, a vehicle stopping indicative signal and a vehicle speed indicative signal. The control unit also connected to an engine idling condition detector switch to receive engine idling condition indicative signal therefrom. The control unit derives vehicular acceleration and compares the vehicular acceleration with a reference value. Also, the control unit detects the vehicle driving condition based on the input parameters. The control unit is active to harden suspension when the following condition is satisfied:
the engine idling condition detector switch is open which is representative of depressed condition of an accelerator pedal;
the brake switch is held open which represents released condition of the brake; and
magnitude of the vehicle acceleration is greater than a predetermined value.
By hardening the suspension system, squat or nose-up which can occur when the vehicle start running or the vehicle accelerates in a magnitude in excess of a given magnitude, is successfully suppressed. In the suspension control system disclosed in the aforementioned Japanese Patent First Publication, the control unit utilizes the engine idling condition detector switch for providing a predetermined delay time for hardening or stiffen the suspension characteristics after the engine idling condition detector switch is opened in view of mechanical lag time in power train. Particularly, the lag time is set about 80 msec.
In such conventional suspension control system, the open condition of the engine idling condition detector switch is used as essential parameter for stiffen or harden the suspension characteristics. Therefore, when the engine idling condition detector switch fails or is damaged, suspension control system becomes impossible.